Recent progress in the pathophysiology and treatment of FSGS recurrence

Clinical characteristics and favorable treatment responses of recurrent focal segmental glomerulosclerosis or steroid-resistant nephrotic syndrome in children after kidney transplantation

BACKGROUND

Recurrence of focal segmental glomerulosclerosis (FSGS) or steroid-resistant nephrotic syndrome (SRNS) after kidney transplant leads to significant morbidity and potentially earlier allograft loss. To date however, reported rates, risk factors and treatment outcomes have varied widely.

METHODS

We applied computational phenotypes to a multicenter aggregation of electronic health records data from 7 large pediatric health systems in the USA, to identify recurrence rates, risk factors, and treatment outcomes. We refined the data collection by chart review.

RESULTS

From > 7 million patients, we compared children with primary FSGS/SRNS who received a kidney transplant between 2009 and 2020 and who either developed recurrence (n = 67/165; 40.6%) or did not (n = 98/165). Serum albumin level at time of transplant was significantly lower and recipient HLA DR7 presence was significantly higher in the recurrence group. By 36 months post-transplant, complete remission occurred in 58.2% and partial remission in 17.9%. Through 6 years post-transplant, no remission after recurrence was associated with an increased risk of allograft loss over time (p < 0.0001), but any remission showed similar allograft survival and function decline to those with no recurrence. Since treatments were used in non-random fashion, using spline curves and multivariable non-linear analyses, complete + partial remission chance was significantly higher with greater plasmapheresis sessions, CTLA4-Ig doses or LDL-apheresis sessions. Only treatment with anti-CD20, CTLA4-Ig agents, or LDL-apheresis sessions were associated with complete remission. Excluding 25 patients with mutations did not significantly change our results.

CONCLUSIONS

Our contemporary high-risk cohort had higher favorable response rates than most prior reports, from combinations of agents.

A multi-institutional study found a possible role of anti-nephrin antibodies in post-transplant focal segmental glomerulosclerosis recurrence

Possible roles of anti-nephrin antibodies in post-transplant recurrent focal segmental glomerulosclerosis (FSGS) have been reported recently. To confirm these preliminary results, we performed a multi-institutional study of 22 Japanese pediatric kidney transplant recipients with FSGS including eight genetic FSGS and 14 non-genetic (presumed primary) FSGS. Eleven of the 14 non-genetic FSGS patients had post-transplant recurrent FSGS. Median (interquartile range) plasma levels of anti-nephrin antibodies in post-transplant recurrent FSGS measured using ELISA were markedly high at 899 (831, 1292) U/mL (cutoff 231 U/mL) before transplantation or during recurrence. Graft biopsies during recurrence showed punctate IgG deposition co-localized with nephrin that had altered localization with increased nephrin tyrosine phosphorylation and Src homology and collagen homology A expressions. Graft biopsies after remission showed no signals for IgG and a normal expression pattern of nephrin. Anti-nephrin antibody levels decreased to 155 (53, 367) U/mL in five patients with samples available after remission. In patients with genetic FSGS as in those with non-genetic FSGS without recurrence, anti-nephrin antibody levels were comparable to those of 30 control individuals, and graft biopsies had no signals for IgG and a normal expression pattern of nephrin. Thus, our results suggest that circulating anti-nephrin antibodies are a possible candidate for circulating factors involved in the pathogenesis of post-transplant recurrent FSGS and that this may be mediated by nephrin phosphorylation. Larger studies including other ethnicities are required to confirm this finding.

Post-transplant recurrence of focal segmental glomerular sclerosis: consensus statements

Focal segmental glomerular sclerosis (FSGS) is 1 of the primary causes of nephrotic syndrome in both pediatric and adult patients, which can lead to end-stage kidney disease. Recurrence of FSGS after kidney transplantation significantly increases allograft loss, leading to morbidity and mortality. Currently, there are no consensus guidelines for identifying those patients who are at risk for recurrence or for the management of recurrent FSGS. Our work group performed a literature search on PubMed/Medline, Embase, and Cochrane, and recommendations were proposed and graded for strength of evidence. Of the 614 initially identified studies, 221 were found suitable to formulate consensus guidelines for recurrent FSGS. These guidelines focus on the definition, epidemiology, risk factors, pathogenesis, and management of recurrent FSGS. We conclude that additional studies are required to strengthen the recommendations proposed in this review.

Current understanding of the molecular mechanisms of circulating permeability factor in focal segmental glomerulosclerosis

The pathogenetic mechanisms underlying the onset and the post-transplant recurrence of primary focal segmental glomerulosclerosis (FSGS) are complex and remain yet to be fully elucidated. However, a growing body of evidence emphasizes the pivotal role of the immune system in both initiating and perpetuating the disease. Extensive investigations, encompassing both experimental models and patient studies, have implicated T cells, B cells, and complement as crucial actors in the pathogenesis of primary FSGS, with various molecules being proposed as potential "circulating factors" contributing to the disease and its recurrence post kidney-transplantation. In this review, we critically assessed the existing literature to identify essential pathways for a comprehensive characterization of the pathogenesis of FSGS. Recent discoveries have shed further light on the intricate interplay between these mechanisms. We present an overview of the current understanding of the engagement of distinct molecules and immune cells in FSGS pathogenesis while highlighting critical knowledge gaps that require attention. A thorough characterization of these intricate immune mechanisms holds the potential to identify noninvasive biomarkers that can accurately identify patients at high risk of post-transplant recurrence. Such knowledge can pave the way for the development of targeted and personalized therapeutic approaches in the management of FSGS.

The podocyte: glomerular sentinel at the crossroads of innate and adaptive immunity

Focal segmental glomerulosclerosis (FSGS) is a common glomerular disorder that manifests clinically with the nephrotic syndrome and has a propensity to recur following kidney transplantation. The pathophysiology and therapies available to treat FSGS currently remain elusive. Since the podocyte appears to be the target of apparent circulating factor(s) that lead to recurrence of proteinuria following kidney transplantation, this article is focused on the podocyte. In the context of kidney transplantation, the performance of pre- and post-reperfusion biopsies, and the establishment of in vitro podocyte liquid biopsies/assays allow for the development of clinically relevant studies of podocyte biology. This has given insight into new pathways, involving novel targets in innate and adaptive immunity, such as SMPDL3b, cGAS-STING, and B7-1. Elegant experimental studies suggest that the successful clinical use of rituximab and abatacept, two immunomodulating agents, in our case series, may be due to direct effects on the podocyte, in addition to, or perhaps distinct from their immunosuppressive functions. Thus, tissue biomarker-directed therapy may provide a rational approach to validate the mechanism of disease and allow for the development of new therapeutics for FSGS. This report highlights recent progress in the field and emphasizes the importance of kidney transplantation and recurrent FSGS (rFSGS) as a platform for the study of primary FSGS.

Decay-Accelerating Factor Expression Modulates the Severity of Experimental Focal Segmental Glomerulosclerosis

Genetically induced decay-accelerating factor (DAF) overexpression prevents adriamycin (ADR)-induced focal segmental glomerulosclerosis (FSGS) in mice. Pharmacologic inhibition of DAF cleavage reduces complement activation in the glomeruli and albuminuria in murine ADR-induced FSGS. Inhibition of complement activation represents a valuable therapeutic strategy for FSGS and, potentially, other glomerular diseases.

Molecular profiling of urinary extracellular vesicles in chronic kidney disease and renal fibrosis

Chronic kidney disease (CKD) is a long-term kidney damage caused by gradual loss of essential kidney functions. A global health issue, CKD affects up to 16% of the population worldwide. Symptoms are often not apparent in the early stages, and if left untreated, CKD can progress to end-stage kidney disease (ESKD), also known as kidney failure, when the only possible treatments are dialysis and kidney transplantation. The end point of nearly all forms of CKD is kidney fibrosis, a process of unsuccessful wound-healing of kidney tissue. Detection of kidney fibrosis, therefore, often means detection of CKD. Renal biopsy remains the best test for renal scarring, despite being intrinsically limited by its invasiveness and sampling bias. Urine is a desirable source of fibrosis biomarkers as it can be easily obtained in a non-invasive way and in large volumes. Besides, urine contains biomolecules filtered through the glomeruli, mirroring the pathological state. There is, however, a problem of highly abundant urinary proteins that can mask rare disease biomarkers. Urinary extracellular vesicles (uEVs), which originate from renal cells and carry proteins, nucleic acids, and lipids, are an attractive source of potential rare CKD biomarkers. Their cargo consists of low-abundant proteins but highly concentrated in a nanosize-volume, as well as molecules too large to be filtered from plasma. Combining molecular profiling data (protein and miRNAs) of uEVs, isolated from patients affected by various forms of CKD, this review considers the possible diagnostic and prognostic value of uEVs biomarkers and their potential application in the translation of new experimental antifibrotic therapeutics.

Benefit of B7-1 staining and abatacept for treatment-resistant post-transplant focal segmental glomerulosclerosis in a predominantly pediatric cohort: time for a reappraisal

BACKGROUND

Primary FSGS manifests with nephrotic syndrome and may recur following KT. Failure to respond to conventional therapy after recurrence results in poor outcomes. Evaluation of podocyte B7-1 expression and treatment with abatacept (a B7-1 antagonist) has shown promise but remains controversial.

METHODS

From 2012 to 2020, twelve patients developed post-KT FSGS with nephrotic range proteinuria, failed conventional therapy, and were treated with abatacept. Nine/twelve (< 21 years old) experienced recurrent FSGS; three adults developed de novo FSGS, occurring from immediately, up to 8 years after KT. KT biopsies were stained for B7-1.

RESULTS

Nine KTRs (75%) responded to abatacept. Seven of nine KTRs were B7-1 positive and responded with improvement/resolution of proteinuria. Two patients with rFSGS without biopsies resolved proteinuria after abatacept. Pre-treatment UPCR was 27.0 ± 20.4 (median 13, range 8-56); follow-up UPCR was 0.8 ± 1.3 (median 0.2, range 0.07-3.9, p < 0.004). Two patients who were B7-1 negative on multiple KT biopsies did not respond to abatacept and lost graft function. One patient developed proteinuria while receiving belatacept, stained B7-1 positive, but did not respond to abatacept.

CONCLUSIONS

Podocyte B7-1 staining in biopsies of KTRs with post-transplant FSGS identifies a subset of patients who may benefit from abatacept. A higher resolution version of the Graphical abstract is available as Supplementary information.

Response to steroid and immunosuppressive therapies may predict post-transplant recurrence of steroid-resistant nephrotic syndrome

BACKGROUND

Recurrence of SRNS is a major challenge in KT. Several clinical factors, including initial steroid sensitivity, have been associated with increased post-transplant SRNS recurrence risk. However, conflicting data have been reported, possibly due to the heterogeneous pathophysiology of SRNS and the lack of genetic testing of SRNS patients. Furthermore, the response to immunosuppressive therapies has not been evaluated.

METHODS

Seventy patients aged 1-15 years at SRNS onset who underwent KT between 2002 and 2018 were enrolled. Patients with secondary, familial, syndromic, and genetic forms of SRNS and those who were not treated with steroid were excluded. This study aimed to assess the risk factors for post-transplant recurrence, including treatment responses to initial steroid therapy and additional therapies with immunosuppressive agents, rituximab, plasmapheresis, and/or LDL-A.

RESULTS

Data from 36 kidney transplant recipients were analyzed. Twenty-two (61%) patients experienced post-transplant SRNS recurrence, while 14 patients did not. The proportion of patients who achieved complete or partial remission with initial steroid therapy and/or additional therapies with immunosuppressive agents, rituximab, plasmapheresis, and/or LDL-A was significantly higher in the SRNS recurrence group (19/22, 86%) than in the group without SRNS recurrence (6/14, 43%; p = .01).

CONCLUSION

This study suggests that the response to steroid treatment, other immunosuppressive agents, rituximab, plasmapheresis, and/or LDL-A may predict post-transplant SRNS recurrence.

STAT-3 signaling role in an experimental model of nephropathy induced by doxorubicin

The focal segmental glomerulosclerosis (FSGS) is one of the most frequent glomerulopathy in the world, being considered a significative public health problem worldwide. The disease is characterized by glomerular loss mainly due to inflammation process and collagen fibers deposition. STAT-3 is a transcription factor associated with cell differentiation, migration and proliferation and in renal cells it has been related with fibrosis, acting on the progression of the lesion. Considering this perspective, the present study evaluated the involvement of STAT-3 molecule in an experimental model of FSGS induced by Doxorubicin (DOX). DOX mimics primary FSGS by causing both glomerular and tubular lesions and the inhibition of the STAT3 pathway leads to a decrease in fibrosis and attenuation of kidney damage. We described here a novel FSGS experimental model in a strain of genetically heterogeneous mice which resembles the reality of FSGS patients. DOX-injected mice presented elevated indices of albuminuria and glycosuria, that were significantly reduced in animals treated with a STAT-3 inhibitor (STATTIC), in addition with a decrease of some inflammatory molecules. Moreover, we detected that SOCS-3 (a regulator of STAT family) was up-regulated only in STATTIC-treated mice. Finally, histopathological analyzes showed that DOX-treated group had a significant increase in a tubulointerstitial fibrosis and tubular necrosis, which were not identified in both control and STATTIC groups. Thus, our results indicate that STAT-3 pathway possess an important role in experimental FSGS induced by DOX and may be an important molecule to be further investigated.

Rituximab, Mycophenolic Acid, and Calcineurin Inhibitors Achieve Long-Term Remission in Pediatric Focal Segmental Glomerulosclerosis with Steroid-Resistant and Frequently Relapsing Nephrotic Syndrome: A Report of Two Cases

Studies investigating the effect of rituximab in children with nephrotic syndrome (NS) due to focal segmental glomerulosclerosis (FSGS) have reported conflicting results, with some concluding that patients may require additional immunosuppressive therapy to achieve and/or maintain long-term remission. We report successful treatment of pediatric FSGS with rituximab infusions, followed by maintenance immunosuppression with mycophenolic acid (MPA) and a calcineurin inhibitor (CNI) in 1 patient with refractory steroid-resistant NS (SRNS), and one with frequently relapsing NS (FRNS). Case 1 is a patient with refractory SRNS due to FSGS. MPA and tacrolimus induced complete remission within 6 months following rituximab treatment. Remission was maintained for over 2 years, and the patient's kidney function and body height also returned to normal ranges within this time. Case 2 is a patient with FRNS due to FSGS, who was treated with rituximab followed by MPA and cyclosporine, which successfully prevented relapses for 18 months, that is, at the end point of the observation. Our case report demonstrates that rituximab and a combination of CNIs and MPA can be effective in achieving complete remission in pediatric refractory SRNS and sustaining remission in pediatric FSGS with FRNS and SRNS for several years. This treatment regimen has the advantage of eliminating the need for long-term high-dose steroid treatments, allowing 1 patient to achieve normal growth and recover from other adverse steroid effects.

Focal segmental glomerulosclerosis: Risk for recurrence and interventions to optimize outcomes following recurrence

BACKGROUND

FSGS is a common indication for kidney transplant with a high-risk of posttransplant recurrence.

METHODS

In this review, we summarize current knowledge about FSGS recurrence after kidney transplantation, including epidemiology, pretransplant planning, posttransplant management, and investigational treatments.

RESULTS

FSGS recurs in 14%-60% of first transplants, likely associated with a circulating permeability factor. Pretransplant counseling regarding recurrence is critical, and patients with FSGS should undergo pretransplant genetic screening. Rapid progression to ESKD, initial steroid responsiveness, younger age at diagnosis, race/ethnicity, and mesangial hypercellularity or minimal change histology on native biopsy may be associated with recurrence. Living donation is not contraindicated but does not result in improved graft survival relative to deceased donation. Pretransplant nephrectomy may be performed for a variety of reasons, but does not decrease recurrence. Pretransplant therapy with rituximab and/or PE is understudied but not clearly effective at preventing recurrence. Patients with FSGS typically present early with rapid-onset severe proteinuria. Diagnosis can be confirmed by biopsy showing foot process effacement; typical FSGS lesions are not seen on light microscopy in the early stages. There is no established effective treatment for recurrent FSGS, but renin-angiotensin-aldosterone system inhibition and extracorporeal therapies, including PE and IA, are most commonly used. Adjunct or alternative therapies may include rituximab, lipopheresis, and cyclosporine.

Unexpected Late Response to Ofatumumab in Adult Post-Transplantation Recurrent Focal Segmental Glomerulosclerosis, Case Report

BACKGROUND

Idiopathic focal segmental glomerulosclerosis is an important cause of kidney failure in adults, which is associated with a high risk of disease recurrence after transplantation. Plasmapheresis, rituximab, immunoadsorption, and high-dose cyclosporine are used to treat post-transplant recurrent focal segmental glomerulosclerosis (rFSGS). However, the response rate is variable, and few options remain for unresponsive patients.

CASE REPORT

We present a 44-year-old man with an early post-transplant rFSGS. After peritransplant plasmapheresis, rituximab, and abatacept treatments failed, we employed ofatumumab. After 9 months without apparent benefit, we observed an unexpected partial remission thereafter, without severe side effects. Furthermore, remission has been sustained in 30-month follow-up.

CONCLUSIONS

We believe ofatumumab can be considered an alternative for patients with plasmapheresis and rituximab-resistant post-transplant rFSGS.

Management of recurrent focal segmental glomerulosclerosis (FSGS) post renal transplantation

BACKGROUND

One of the common GN causing ESKD is focal segmental glomerulosclerosis (FSGS). Recurrence of FSGS post-transplantation can lead to graft loss. Data on management either prophylactically or once recurrence occurs are limited. This review article aims to assess the effective management of patients with FSGS recurrence post-transplantation, looking mainly at recurrence post prophylactic treatment and remission in case of treatment post recurrence.

METHODS

Twenty-three studies were included using the search MeSH terms "FSGS" "recurrence" "adults" "transplantation" "treatment". Search engines used were Pubmed, clinical key, Scopus and Cochrane library. Inclusion criteria were articles covered adult patients with recurrent FSGS post renal transplantation, treatment with rituximab and plasmapheresis, and articles published from 2000 tt2021. Excluded articles were paediatric population, studies with no reported outcomes of the treatment of FSGS, and Patients who received stem cell transplantation or galactose therapy.

RESULTS

Prophylactic PP did not show a reduction in recurrence of FSGS in 2/3 studies. Prophylactic rituximab was shown to reduce recurrence of FSGS in one-study and case reports. Treatment of recurrent FSGS with PP showed responses ranging from 41% to 100%. Only one study did not show improvement with PP use as treatment having a 27% remission. Treatment with rituximab showed variable results, with reports showing remission ranging from 57% to 100%. Whereas other reports showing no response at all. PP prescription reporting was variable. One study suggested intensified PP regimen while in most other studies PP was guided by the response reflected by the reduction of proteinuria.

DISCUSSION

Reviewing the treatment of recurrent FSGS is crucial, as there no consensus on treating FSGS as the disease is not very common in the adult population. The evidence of different modalities is based on small cohort studies. This paper supports the use of PP and RTX as treatment of recurrent FSGS.

CONCLUSIONS

In conclusion, PP and RTX are the main modalities to treat recurrent FSGS with varying response rates. Prophylactic PP does not play a role in preventing recurrent FSGS. Prophylactic rituximab might play a role in preventing FSGS post-transplantation. PP and RTX, when used as a treatment, show variable response rates. Larger RCTs are needed to have a strong level of evidence to base our clinical management on.

Exosomes: Emerging Therapy Delivery Tools and Biomarkers for Kidney Diseases

Exosomes are nanometer-sized small EVs coated with bilayer structure, which are released by prokaryotic and eukaryotic cells. Exosomes are rich in a variety of biologically active substances, such as proteins, nucleotides, and lipids. Exosomes are widely present in various body fluids and cell culture supernatants, and it mediates the physiological and pathological processes of the body through the shuttle of these active ingredients to target cells. In recent years, studies have shown that exosomes from a variety of cell sources can play a beneficial role in acute and chronic kidney disease. In particular, exosomes derived from mesenchymal stem cells have significant curative effects on the prevention and treatment of kidney disease in preclinical trials. Besides, some encapsulated substances are demonstrated to exert beneficial effects on various diseases, so they have attracted much attention. In addition, exosomes have extensive sources, stable biological activity, and good biocompatibility and are easy to store and transport; these advantages endow exosomes with superior diagnostic value. With the rapid development of liquid biopsy technology related to exosomes, the application of exosomes in the rapid diagnosis of kidney disease has become more prominent. In this review, the latest development of exosomes, including the biosynthesis process, the isolation and identification methods of exosomes are systematically summarized. The utilization of exosomes in diagnosis and their positive effects in the repair of kidney dysfunction are discussed, along with the specific mechanisms. This review is expected to be helpful for relevant studies and to provide insight into future applications in clinical practice.

Rituximab for recurrence of primary focal segmental glomerulosclerosis after kidney transplantation: Results of a nationwide study

Rituximab (RTX) therapy for primary focal segmental glomerulosclerosis recurrence after kidney transplantation (KT) has been extensively debated. We aimed to assess the benefit of adding RTX to plasmapheresis (PP), corticosteroids, and calcineurin inhibitors (standard of care, SOC). We identified 148 adult patients who received KT in 12/2004-12/2018 at 21 French centers: 109 received SOC (Group 1, G1), and 39 received immediate RTX along with SOC (Group 2, G2). In G1, RTX was introduced after 28 days of SOC in the event of failure (G1a, n = 19) or PP withdrawal (G1b, n = 12). Complete remission (CR) was achieved in 46.6% of patients, and partial remission (PR) was achieved in 33.1%. The 10-year graft survival rates were 64.7% and 17.9% in responders and nonresponders, respectively. Propensity score analysis showed no difference in CR+PR rates between G1 (82.6%) and G2 (71.8%) (p = .08). Following the addition of RTX (G1a), 26.3% of patients had CR, and 31.6% had PR. The incidence of severe infections was similar between patients treated with and without RTX. In multivariable analysis, infection episodes were associated with hypogammaglobulinemia <5 g/L. RTX could be used in cases of SOC failure or remission for early discontinuation of PP without increasing the risk of infection.

Amount and selectivity of proteinuria may predict the treatment response in post-transplant recurrence of focal segmental glomerulosclerosis: a single-center retrospective study

BACKGROUND

Primary focal segmental glomerulosclerosis (FSGS) frequently recurs after kidney transplantation and is associated with poor graft survival. To date, few studies have investigated predictive factors for treatment responses in recurrent FSGS.

METHODS

We retrospectively analyzed 16 patients who were < 16 years at the age of onset and had post-transplant recurrence of FSGS from 1993 to 2018. Patients who achieved complete remission or partial remission after initiating therapy for recurrent FSGS were defined as responders. We compared several clinical characteristics between responders and non-responders. Time to remission was also analyzed.

RESULTS

Ten patients were responders, and six patients were non-responders. Univariate analysis showed that responders had a significantly lower amount of maximum proteinuria at the time of recurrence (P = 0.015) and more highly selective proteinuria (P = 0.013) than non-responders. The time to remission from initiation of therapy was 2 months (interquartile range 0.2-4.4). In all responders, except for one patient, remission was achieved within 6 months.

CONCLUSIONS

Therapeutic responses may be predicted by examining the amount and selectivity of proteinuria at the time of recurrence. Further studies with larger numbers of patients are clearly required to validate these findings.

A Phase 1 first-in-human study of the safety, tolerability, and pharmacokinetics of the ROBO2 fusion protein PF-06730512 in healthy participants

Proteinuria associated with podocyte effacement is a hallmark of focal segmental glomerulosclerosis (FSGS). Preclinical studies implicated ROBO2/SLIT2 signaling in the regulation of podocyte adhesion, and inhibition of this pathway is a novel target to slow FSGS disease progression. This first-in-human dose-escalation study evaluated the safety, tolerability, pharmacokinetics, and immunogenicity of PF-06730512, an Fc fusion protein that targets the ROBO2/SLIT2 pathway, in healthy adults. In this Phase 1, double-blind, sponsor-open study, single ascending dose (SAD) cohorts were randomized to receive up to 1000 mg or placebo intravenously (IV); multiple ascending dose (MAD) cohorts were randomized to receive up to 400 mg subcutaneous (SC) doses, 1000 mg IV dose, or matching placebo. Safety evaluations were performed up to 71 (SAD) and 113 (MAD) days after dosing; blood samples were collected to measure serum PF-06730512 concentrations and antidrug antibodies (ADA) to PF-06730512. Seventy-nine participants (SAD, 47; MAD, 32) were enrolled. There were 108 mild (SAD, 46; MAD, 62) and 21 moderate (SAD, 13; MAD, 8) treatment-emergent adverse events (TEAEs); no deaths, treatment-related serious AEs, severe TEAEs, or infusion reactions were reported. PF-06730512 exposure generally increased in an approximately dose-proportional manner; mean t1/2 ranged from 12-15 days across 50-1000 mg doses. Immunogenicity incidence was low (SAD, 0 ADA+; MAD, 2 ADA+). In conclusion, single IV doses of PF-06730512 up to 1000 mg and multiple IV and SC dosing up to 1000 and 400 mg, respectively, were safe and well tolerated in healthy participants. Further trials in patients with FSGS are warranted. Clinical trial registration: Clinicaltrials.gov: NCT03146065.

Endothelin-targeted new treatments for proteinuric and inflammatory glomerular diseases: focus on the added value to anti-renin-angiotensin system inhibition

Chronic kidney disease (CKD) is the main cause of end-stage renal disease worldwide arising as a frequent complication of diabetes, obesity, and hypertension. Current therapeutic options, mainly based of inhibition of the renin-angiotensin system (RAS), provide imperfect renoprotection if started at an advanced phase of the disease, and treatments that show or even reverse the progression of CKD are needed. The endothelin (ET) system contributes to the normal renal physiology; however, robust evidence suggests a key role of ET-1 and its cognate receptors, in the progression of CKD. The effectiveness of ET receptor antagonists in ameliorating renal hemodynamics and fibrosis has been largely demonstrated in different experimental models. A significant antiproteinuric effect of ET receptor antagonists has been found in diabetic and non-diabetic CKD patients even on top of RAS blockade, and emerging evidence from ongoing clinical trials highlights their beneficial effects on a wide range of kidney disorders.

Loss of decay-accelerating factor triggers podocyte injury and glomerulosclerosis

Kidney glomerulosclerosis commonly progresses to end-stage kidney failure, but pathogenic mechanisms are still poorly understood. Here, we show that podocyte expression of decay-accelerating factor (DAF/CD55), a complement C3 convertase regulator, crucially controls disease in murine models of adriamycin (ADR)-induced focal and segmental glomerulosclerosis (FSGS) and streptozotocin (STZ)-induced diabetic glomerulosclerosis. ADR induces enzymatic cleavage of DAF from podocyte surfaces, leading to complement activation. C3 deficiency or prevention of C3a receptor (C3aR) signaling abrogates disease despite DAF deficiency, confirming complement dependence. Mechanistic studies show that C3a/C3aR ligations on podocytes initiate an autocrine IL-1β/IL-1R1 signaling loop that reduces nephrin expression, causing actin cytoskeleton rearrangement. Uncoupling IL-1β/IL-1R1 signaling prevents disease, providing a causal link. Glomeruli of patients with FSGS lack DAF and stain positive for C3d, and urinary C3a positively correlates with the degree of proteinuria. Together, our data indicate that the development and progression of glomerulosclerosis involve loss of podocyte DAF, triggering local, complement-dependent, IL-1β–induced podocyte injury, potentially identifying new therapeutic targets.

NPHS2 gene polymorphism aggravates renal damage caused by focal segmental glomerulosclerosis with COL4A3 mutation

Focal segmental glomerulosclerosis (FSGS), a type of primary glomerular disease, is the leading cause of end-stage renal disease (ESRD). Several studies have revealed that certain single-gene mutations are involved in the pathogenesis of FSGS; however, the main cause of FSGS has not been fully elucidated. Homozygous mutations in the glomerular basement membrane gene can lead to early renal failure, while heterozygous carriers develop renal failure symptoms late. Here, molecular genetic analysis of clinical information collected from clinical reports and medical records was performed. Results revealed that nephrosis 2 (NPHS2) gene polymorphism aggravated renal damage in three FSGS families with heterozygous COL4A3 mutation, leading to early renal failure in index patients. Our findings suggest that COL4A3 and NPHS2 may have a synergistic effect on renal injury caused by FSGS. Further analysis of the glomerular filtration barrier could help assess the cause of kidney damage. Moreover, a detailed analysis of the glomerular basement membrane-related genes and podocyte structural proteins may help us better understand FSGS pathogenesis and provide insights into the prognosis and treatment of hereditary glomerulonephropathy.

Challenges in primary focal segmental glomerulosclerosis diagnosis: from the diagnostic algorithm to novel biomarkers

Primary or idiopathic focal segmental glomerulosclerosis (FSGS) is a kidney entity that involves the podocytes, leading to heavy proteinuria and in many cases progresses to end-stage renal disease. Idiopathic FSGS has a bad prognosis, as it involves young individuals who, in a considerably high proportion (∼15%), are resistant to corticosteroids and other immunosuppressive treatments as well. Moreover, the disease recurs in 30–50% of patients after kidney transplantation, leading to graft function impairment. It is suspected that this relapsing disease is caused by a circulating factor(s) that would permeabilize the glomerular filtration barrier. However, the exact pathologic mechanism is an unsettled issue. Besides its poor outcome, a major concern of primary FSGS is the complexity to confirm the diagnosis, as it can be confused with other variants or secondary forms of FSGS and also with other glomerular diseases, such as minimal change disease. New efforts to optimize the diagnostic approach are arising to improve knowledge in well-defined primary FSGS cohorts of patients. Follow-up of properly classified primary FSGS patients will allow risk stratification for predicting the response to different treatments. In this review we will focus on the diagnostic algorithm used in idiopathic FSGS both in native kidneys and in disease recurrence after kidney transplantation. We will emphasize those potential confusing factors as well as their detection and prevention. In addition, we will also provide an overview of ongoing studies that recruit large cohorts of glomerulopathy patients (Nephrotic Syndrome Study Network and Cure Glomerulonephropathy, among others) and the experimental studies performed to find novel reliable biomarkers to detect primary FSGS.

Recurrence of FSGS after Kidney Transplantation in Adults

BACKGROUND AND OBJECTIVES

FSGS recurrence after kidney transplantation is a major risk factor for graft loss. However, the natural history, clinical predictors, and response to treatment remain unclear because of small sample sizes and poor generalizability of single-center studies, and disease misclassification in registry-based studies. We therefore aimed to determine the incidence, predictors, and treatment response of recurrent FSGS in a large cohort of kidney transplant recipients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The Post-Transplant Glomerular Disease (TANGO) project is an observational, multicenter, international cohort study that aims to investigate glomerular disease recurrence post-transplantation. Transplant recipients were screened for the diagnosis of idiopathic FSGS between 2005 and 2015 and details were recorded about the transplant, clinical outcomes, treatments, and other risk factors.

RESULTS

Among 11,742 kidney transplant recipients screened for FSGS, 176 had a diagnosis of idiopathic FSGS and were included. FSGS recurred in 57 patients (32%; 95% confidence interval [95% CI], 25% to 39%) and 39% of them lost their graft over a median of 5 (interquartile range, 3.0-8.1) years. Multivariable Cox regression revealed a higher risk for recurrence with older age at native kidney disease onset (hazard ratio [HR], 1.37 per decade; 95% CI, 1.09 to 1.56). Other predictors were white race (HR, 2.14; 95% CI, 1.08 to 4.22), body mass index at transplant (HR, 0.89 per kg/m²; 95% CI, 0.83 to 0.95), and native kidney nephrectomies (HR, 2.76; 95% CI, 1.16 to 6.57). Plasmapheresis and rituximab were the most frequent treatments (81%). Partial or complete remission occurred in 57% of patients and was associated with better graft survival.

CONCLUSIONS

Idiopathic FSGS recurs post-transplant in one third of cases and is associated with a five-fold higher risk of graft loss. Response to treatment is associated with significantly better outcomes but is achieved in only half of the cases.

LDL-apheresis-induced remission of focal segmental glomerulosclerosis recurrence in pediatric renal transplant recipients

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) in pediatric patients is typically difficult to treat and will progress to end-stage renal disease (ESRD) in about 10% of cases. Following kidney transplantation, FSGS can recur in up to 56% of renal allografts-with a near 100% recurrence in subsequent transplants.

METHODS

Four different pediatric centers across the USA and the UK employed a protocol using LDL-apheresis (LDL-A) and pulse solumedrol to treat recurrent FSGS after transplantation in seven patients. All the patients included in this series demonstrated immediate, or early, recurrence of FSGS, which clinically presented as nephrotic-range proteinuria within hours to days after implantation of the kidney.

RESULTS

All patients experienced reductions in urinary protein to creatinine ratios resulting in partial or complete remission. All patients demonstrated improvements in their estimated GFRs at their most recent follow-up since LDL-A discontinuation.

CONCLUSIONS

This case series describes the successful treatment, across four different pediatric centers, of seven pediatric patients with recurrent post-transplant FSGS using the Liposorber® LA-15 in combination with pulse solumedrol.

Therapeutic apheresis in kidney transplantation: An updated review

Therapeutic apheresis is a cornerstone of therapy for several conditions in transplantation medicine and is available in different technical variants. In the setting of kidney transplantation, immunological barriers such as ABO blood group incompatibility and preformed donor-specific antibodies can complicate the outcome of deceased- or living- donor transplantation. Postoperatively, additional problems such as antibody-mediated rejection and a recurrence of primary focal segmental glomerulosclerosis can limit therapeutic success and decrease graft survival. Therapeutic apheresis techniques find application in these issues by separating and selectively removing exchanging or modifying pathogenic material from the patient by an extracorporeal aphaeresis system. The purpose of this review is to describe the available techniques of therapeutic aphaeresis with their specific advantages and disadvantages and examine the evidence supporting the application of therapeutic aphaeresis as an adjunctive therapeutic option to immunosuppressive agents in protocols before and after kidney transplantation.

Recurrent and de novo Glomerulonephritis After Kidney Transplantation

The prevalence, pathogenesis, predictors, and natural course of patients with recurrent glomerulonephritis (GN) occurring after kidney transplantation remains incompletely understood, including whether there are differences in the outcomes and advances in the treatment options of specific GN subtypes, including those with de novo GN. Consequently, the treatment options and approaches to recurrent disease are largely extrapolated from the general population, with responses to these treatments in those with recurrent or de novo GN post-transplantation poorly described. Given a greater understanding of the pathogenesis of GN and the development of novel treatment options, it is conceivable that these advances will result in an improved structure in the future management of patients with recurrent or de novo GN. This review focuses on the incidence, genetics, characteristics, clinical course, and risk of allograft failure of patients with recurrent or de novo GN after kidney transplantation, ascertaining potential disparities between “high risk” disease subtypes of IgA nephropathy, idiopathic membranous glomerulonephritis, focal segmental glomerulosclerosis, and membranoproliferative glomerulonephritis. We will examine in detail the management of patients with high risk GN, including the pre-transplant assessment, post-transplant monitoring, and the available treatment options for disease recurrence. Given the relative paucity of data of patients with recurrent and de novo GN after kidney transplantation, a global effort in collecting comprehensive in-depth data of patients with recurrent and de novo GN as well as novel trial design to test the efficacy of specific treatment strategy in large scale multicenter randomized controlled trials are essential to address the knowledge deficiency in this disease.

Risk factors associated with allograft failure in pediatric kidney transplant recipients with focal segmental glomerulosclerosis

BACKGROUND

With improved outcomes for children transplanted with FSGS since previous NAPRTCS registry reports, this study re-evaluates the association of living donation, immunosuppression, and DGF on graft survival.

SETTING

Patients transplanted between 2002 and 2016, comparing FSGS diagnosis vs other glomerular diseases.

METHODS

Primary outcomes were allograft survival and FSGS recurrent-free graft survival. Potential risk factors were obtained at the time of transplant and up to 30 days post-transplantation. Analysis considered a priori that DGF may be a proxy for severe FSGS recurrence. Multivariable survival models for outcome were tested for sensitivity without/with DGF to determine features independent of recurrence.

RESULTS

From the larger cohort of 3010 patients, 5-year graft survival in children with FSGS (n = 455) was worse (74.3%) compared with other glomerular diseases (87.1%, n = 690) (HR 1.45, P = 0.033). Modeling all glomerular diseases, survival risk was associated with deceased donor (HR 1.83, P = 0.002), re-transplantation (HR 1.58, P = 0.013), and recipient age (HR 1.06/y, P = 0.002). The living donor advantage was not confirmed in a FSGS model (HR 1.51 for deceased, P = 0.12). DGF was highly associated with graft failure (HR 4.39, P < 0.001) and independent of re-transplant history but not FSGS diagnosis. Induction agents or primary immunosuppression choices were not associated with survival.

CONCLUSION

Graft survival rates have improved since the previous report. Living donor did not predict graft failure, but there remains no survival advantage. DGF was the primary independent predictor for graft loss secondary to FSGS recurrence, consistent with DGF being a proxy for severe recurrent disease.

Disease Recurrence-The Sword of Damocles in Kidney Transplantation for Primary Focal Segmental Glomerulosclerosis

A major obstacle in kidney transplantation for primary focal segmental glomerulosclerosis (FSGS) is the risk of disease recurrence. Recurrent FSGS affects up to 60% of first kidney grafts and exceeds 80% in patients who have lost their first graft due to recurrent FSGS. Clinical and experimental evidence support the hypothesis that a circulating permeability factor is the mediator in the pathogenesis of primary and recurrent disease. Despite all efforts, the causing agent has not yet been identified. Several treatment options for the management of recurrent FSGS have been proposed. In addition to plasma exchange, B-cell depleting antibodies are effective in recurrent FSGS. This indicates, that the secretion and/or activity of the postulated circulating permeability factor(s) may be B-cell related. This review summarizes the current knowledge on permeability factor(s) possibly related to the disease and discusses strategies for the management of recurrent FSGS. These include profound B-cell depletion prior to transplantation, as well as the salvage of an allograft affected by recurrent FSGS by transfer into a second recipient.

Clinical features and outcomes of kidney transplant recipients with focal segmental glomerulosclerosis recurrence

AIM

Focal segmental glomerulosclerosis recurs in up to 30% and up to 80% of adult and pediatric kidney transplant recipients, respectively. There is no standard of care treatment. The purpose of this study was to evaluate clinical characteristics, treatments and outcomes of patients with focal segmental glomerulosclerosis recurrence (FSGSr).

METHODS

This was a retrospective single-center cohort study including FSGSr patients treated with plasmapheresis (PP) and combinations of high dose steroids, cyclosporine and rituximab.

RESULTS

Among 61 patients included in this analysis the median time to diagnosis was 19 days. The incidence of first biopsy-confirmed FSGSr was 18% reaching 52.4% with follow-up biopsies. During PP treatment 54% of the patients developed infectious complications. PP was discontinued in 37% of patients due to treatment failure (no remission or graft loss) and in 26% due to an adverse event. All patients who discontinued PP due to adverse event did not show clinical response or lost the allograft. The incidence of acute rejection was 34.4%. The incidences of partial and complete remissions were 16.4% and 27.8%, respectively. Overall 6-years patient and graft survivals were 90.7% and 64.5%, respectively.

CONCLUSION

This analysis confirms the low, variable and unpredictable rate of FSGSr remission, inconsistencies among available therapeutic options and its high rate of adverse events, and the negative impact on graft survival.

Evaluation of the Diagnostic Potential of uPAR as a Biomarker in Renal Biopsies of Patients with FSGS

Minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS) are primary glomerulopathies leading to proteinuria, known as podocytopathies, which share syndromic and morphological similarities. Morphological similarity occurs in cases of FSGS in which the sclerotic lesion was not sampled in renal biopsy, due to the focal nature of the disease. Differentiating these entities is very important, especially in cases of suspected FSGS but with sclerotic lesion not sampled, as they are diseases that apparently have different pathogenic mechanisms and prognosis. The difference in uPAR expression in situ among these two entities may be related to a distinct molecular mechanism involved in pathogenesis. Thus, finding biomarkers involved in the pathogenesis and that can also help in differential diagnosis is very relevant. The aim of this work was to evaluate the potential of urokinase-type plasminogen activator receptor (uPAR) as a biomarker in renal biopsies of patients with podocytopathies (n = 38). Immunohistochemistry showed that FSGS (n = 22) had increased uPAR expression in podocytes compared with both the MCD group (n = 16; p = 0.0368) and control group (n = 21; p = 0.0076). ROC curve (p = 0.008) showed that this biomarker has 80.95% of specificity in biopsies of patients with FSGS. Therefore, uPAR presented a high specificity in cases of podocytopathies associated with sclerosis and it can be considered a potential biomarker for FSGS.

Rituximab as a Preemptive Treatment to Prevent Recurrence of Primary Focal Segmental Glomerulosclerosis: A Novel Approach

OBJECTIVES

Primary idiopathic focal segmental glomerulo-sclerosis is a serious disease, frequently progressing to end-stage kidney failure. Management of recurrence after kidney transplant is challenging despite multiple proposed therapeutic approaches. Available treatment for focal segmental glomeru-losclerosis recurrence is plasma exchange, intravenous cyclosporine, and rituximab. In this study, we investigated kidney transplant recipients with focal segmental glomerulosclerosis who were at high risk for recurrence. Patients were given preemptive rituximab at day 0 posttransplant.

MATERIALS AND METHODS

Between January 2013 and June 2017, our center had 8 patients with primary focal segmental glomerulosclerosis at high risk for recurrence who were scheduled for kidney transplant. These patients received a single rituximab infusion of 375 mg/m2 on day 0 posttransplant. Recurrence of focal segmental glomerulosclerosis posttransplant was defined as repeated proteinuria > 2 g/day, without evidence of clinical or biopsy-proven rejection.

RESULTS

Follow-up showed that none of our patients had immediate posttransplant proteinuria. Only 1 patient developed proteinuria at almost 4 months posttransplant. Mean follow-up duration was 8 months. With regard to complications, 2 patients had serious bacterial infections and 1 patient had cytomegalovirus infection.

CONCLUSIONS

Rituximab at day 0 posttransplant may be used safely to prevent focal segmental glomeru-losclerosis recurrence in the graft in the early posttransplant period. However, longer follow-up studies with larger series are needed.

The elusive podocyte crossmatch for recurrent focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis is a glomerular disorder with a high rate of recurrence. Although kidney biopsies remain the gold standard to diagnose recurrent focal segmental glomerulosclerosis, non-invasive prognostic assays could facilitate preventive treatments and offer insight into disease pathogenicity and heterogeneity. Srivastava et al. describe a simple, cell-based assay to predict recurrence of focal segmental glomerulosclerosis. Although the study needs to be optimized and validated, its novelty is that it does not depend on the specificity of a given permeability factor.

Kidney Injury by Variants in the COL4A5 Gene Aggravated by Polymorphisms in Slit Diaphragm Genes Causes Focal Segmental Glomerulosclerosis

Kidney injury due to focal segmental glomerulosclerosis (FSGS) is the most common primary glomerular disorder causing end-stage renal disease. Homozygous mutations in either glomerular basement membrane or slit diaphragm genes cause early renal failure. Heterozygous carriers develop renal symptoms late, if at all. In contrast to mutations in slit diaphragm genes, hetero- or hemizygous mutations in the X-chromosomal COL4A5 Alport gene have not yet been recognized as a major cause of kidney injury by FSGS. We identified cases of FSGS that were unexpectedly diagnosed: In addition to mutations in the X-chromosomal COL4A5 type IV collagen gene, nephrin and podocin polymorphisms aggravated kidney damage, leading to FSGS with ruptures of the basement membrane in a toddler and early renal failure in heterozygous girls. The results of our case series study suggest a synergistic role for genes encoding basement membrane and slit diaphragm proteins as a cause of kidney injury due to FSGS. Our results demonstrate that the molecular genetics of different players in the glomerular filtration barrier can be used to evaluate causes of kidney injury. Given the high frequency of X-chromosomal carriers of Alport genes, the analysis of genes involved in the organization of podocyte architecture, the glomerular basement membrane, and the slit diaphragm will further improve our understanding of the pathogenesis of FSGS and guide prognosis of and therapy for hereditary glomerular kidney diseases.

Therapeutic Plasma Exchange in Renal Disorders

Nephrologists use hemodialysis and hemofiltration to remove low molecular weight toxic constituents, and increasingly deploy therapeutic plasma exchange (TPE)/plasmapheresis to eliminate higher molecular weight substances such as immunoglobulins or immune complexes from plasma. This review discusses different modalities of TPE, their application in renal disorders, its rationale and complications. TPE is recommended based on evidence, in alloantibody-mediated diseases such as humoral antibody mediated renal transplant rejection, autoantibody mediated glomerulonephritis (GN) disorders for example, anti-glomerular basement membrane GN, as well as in antineutrophil cytoplasmic antibody mediated GN and antibody mediated thrombotic thrombocytopenic purpura. In many other renal illnesses, the rational use of TPE is gaining currency. Double membrane filtration, immune adsorption and cryofiltration are important modifications in TPE

Successful Treatment of Focal Segmental Glomerulosclerosis Recurrence in a Second Kidney Transplant Patient: A Case Report

BACKGROUND

Recurrence of focal segmental glomerulosclerosis (FSGS) in renal allograft recipients after first transplant occurs in the second graft in virtually all patients. There is little evidence regarding optimal treatment.

CASE PRESENTATION

A 55-year-old man with primary FSGS and disease recurrence in both the first and the second kidney grafts is presented. In 1999, the patient developed FSGS 3 years after transplant, which was treated with plasmapheresis and cyclophosphamide. Hemodialysis was started at 8 years from the onset of relapse. In February 2014, the patient received a second kidney transplant, and after 2 weeks laboratory analysis showed nephrotic proteinuria (5.9 g/d) with increased serum creatinine. Biopsy results revealed recurrence of FSGS. At that time, he was treated with steroids and plasmapheresis with partial efficacy, achieving a serum creatinine level of 1.1 mg/dL with decreased proteinuria (1 g/d). After 4 months, creatinine worsened (1.6 mg/dL) with new evidence of proteinuria. Second biopsy results showed evidence of FSGS progression. The patient then received plasmapheresis and 2 doses of rituximab. Follow-up was characterized by progressive remission up to complete resolution. The patient is currently free from relapses after 3 years with good renal function and almost no proteinuria.

CONCLUSIONS

More evidence and prospective studies are needed to better understand the role of rituximab in FSGS in order to obtain an optimized therapeutic protocol for recurrence of FSGS in renal transplant recipients.

Monitoring suPAR levels in post-kidney transplant focal segmental glomerulosclerosis treated with therapeutic plasma exchange and rituximab

BACKGROUND

Therapeutic plasma exchange (TPE) is an important therapy for recurrent focal segmental glomerulosclerosis (rFSGS) post kidney transplant. suPAR has been causally implicated in rFSGS, and shown to be a unique biomarker for the occurrence and progression of chronic kidney disease. This study was targeted to evaluate the application of monitoring suPAR in TPE treated rFSGS.

METHODS

A retrospective (n = 19) and a prospective (n = 15) cohort of post transplant FSGS patients treated with TPE and rituximab were enrolled. We measured serum suPAR levels before and after the combined therapies, and assessed the role of suPAR changes on proteinuria reduction and podocyte β3- integrin activity.

RESULTS

Treatment with TPE and rituximab resulted in significant decrease in proteinuria and suPAR levels. Among the variables including baseline suPAR, serum creatinine, proteinuria, eGFR, age at diagnosis, age at transplantation, transplantation numbers, time to recurrence, and TPE course numbers, only the reduction in suPAR levels and baseline proteinuria significantly correlated with the changes in proteinuria after treatment, with the former performed better in predicting proteinuria alteration. Additionally, the mean podocyte β3 integrin activity significantly decreased after TPE and rituximab treatment (1.10 ± 0.08) as compared to before treatment (1.34 ± 0.08), p < 0.05. Only the reduction in suPAR predicted the response to therapies with an odds ratio of 1.43, 95% CI (1.02, 2.00), p < 0.05.

CONCLUSIONS

Serum suPAR levels reduced significantly after TPE and rituximab treatment in post transplant FSGS patients. The reduction in suPAR levels may be utilized to assess the changes in proteinuria and monitor the response to the therapies. Larger, multi-centered prospective studies monitoring serum suPAR levels in TPE managed post transplant FSGS are warranted.

Apolipoprotein A-Ib as a biomarker of focal segmental glomerulosclerosis recurrence after kidney transplantation: diagnostic performance and assessment of its prognostic value - a multi-centre cohort study

Recurrence of idiopathic focal segmental glomerulosclerosis (FSGS) is a serious complication after kidney transplantation. FSGS relapse is suspected by a sudden increase in proteinuria but there is not an accurate noninvasive diagnostic tool to confirm this entity or to detect patients at risk. We aimed to validate the diagnostic performance of ApoA-Ib to detect FSGS relapses by measuring urinary ApoA-Ib in a retrospective cohort of 61 kidney transplanted patients (37 FSGS and 24 non-FSGS). In addition, to assess the ApoA-Ib predictive ability, ApoA-Ib was measured periodically in a prospective cohort of 13 idiopathic FSGS patients who were followed during 1 year after transplantation. ApoA-Ib had a sensitivity of 93.3% and a specificity of 90.9% to diagnose FSGS relapses, with a high negative predictive value (95.2%), confirming our previous results. In the prospective cohort, ApoA-Ib predated the recurrence in four of five episodes observed. In the nonrelapsing group (n = 9), ApoA-Ib was negative in 37 of 38 samples. ApoA-Ib has the potential to be a good diagnostic biomarker of FSGS relapses, providing a confident criterion to exclude false positives even in the presence of high proteinuria. It has also the potential to detect patients at risk of relapse, even before transplantation.

Non-invasive staging of chronic kidney allograft damage using urine metabolomic profiling

Chronic kidney allograft damage is characterized by IFTA and GS. We sought to identify urinary metabolite signatures associated with severity of IFTA and GS in pediatric kidney transplant recipients. Urine samples (n = 396) from 60 pediatric transplant recipients were obtained at the time of kidney biopsy and assayed for 133 metabolites by mass spectrometry. Metabolite profiles were quantified via PLS-DA. We used mixed-effects regression to identify laboratory and clinical predictors of histopathology. Urine samples (n = 174) without rejection or AKI were divided into training/validation sets (75:25%). Metabolite classifiers trained on IFTA severity and %GS showed strong statistical correlation (r = .73, P < .001 and r = .72; P < .001, respectively) and remained significant on the validation sets. Regression analysis identified additional clinical features that improved prediction: months post-transplant (GS, IFTA); and proteinuria, GFR, and age (GS only). Addition of clinical variables improved performance of the %GS classifier (AUC = 0.9; 95% CI = 0.85-0.96) but not for IFTA (AUC = 0.82; 95% CI = 0.71-0.92). Despite the presence of potentially confounding phenotypes, these findings were further validated in samples withheld for rejection or AKI. We identify urine metabolite classifiers for IFTA and GS, which may prove useful for non-invasive assessment of histopathological damage.

[Current insights about recurrence of glomerular diseases after renal transplantation]

Recurrence of glomerular disease after renal transplantation is a frequent cause of graft loss. Incidence, risk factors and outcome of recurrence are widely due to the underlying glomerular disease. Graft biopsy analysis is required to confirm the definitive diagnosis of recurrence and to start an appropriate therapy that, in some cases, remains challenging to prevent graft failure. Increased use of protocol biopsy and recent advances in our understanding of the pathogenesis of some glomerular diseases with the identification of some relevant biomarkers provide a unique opportunity to initiate kidney-protective therapy at early stages of recurrence on the graft. This review summarizes our current knowledge on the management of many recurrent primary and secondary glomerulonephritis after kidney transplantation.

Recurrence of primary glomerulonephritis: Review of the current evidence

In view of the availability of new immunosuppression strategies, the recurrence of allograft glomerulonephritis (GN) are reported to be increasing with time post transplantation. Recent advances in understanding the pathogenesis of the GN recurrent disease provided a better chance to develop new strategies to deal with the GN recurrence. Recurrent GN diseases manifest with a variable course, stubborn behavior, and poor response to therapy. Some types of GN lead to rapid decline of kidney function resulting in a frustrating return to maintenance dialysis. This subgroup of aggressive diseases actually requires intensive efforts to ascertain their pathogenesis so that strategy could be implemented for better allograft survival. Epidemiology of native glomerulonephritis as the cause of end-stage renal failure and subsequent recurrence of individual glomerulonephritis after renal transplantation was evaluated using data from various registries, and pathogenesis of individual glomerulonephritis is discussed. The following review is aimed to define current protocols of the recurrent primary glomerulonephritis therapy.

Application of next-generation sequencing technology to diagnosis and treatment of focal segmental glomerulosclerosis

A broad range of genetic and non-genetic factors can lead to kidney injury that manifests as focal segmental glomerulosclerosis (FSGS), which can be classified into primary (idiopathic) and secondary forms. Previous genetic approaches to familial or sporadic cases of FSGS or steroid-resistant nephrotic syndrome identified causal mutations in a subset of genes. Recently, next-generation sequencing (NGS) approaches are becoming a part of a standard assessment in medical genetics. Current knowledge of the comprehensive genomic information is changing the way we think about FSGS and draws attention not only to identification of novel causal genes, but also to potential roles for combinations of mutations in multiple genes, mutations with complex inheritance, and susceptibility genes with variable penetrance carrying relatively minor but significant effects. This review provides an update on recent advances in the genetic analysis of FSGS and highlights the potential as well as the new challenges of NGS for diagnosis and mechanism-based treatment of FSGS.

Complement in Non-Antibody-Mediated Kidney Diseases

The complement system is part of the innate immune response that plays important roles in protecting the host from foreign pathogens. The complement components and relative fragment deposition have long been recognized to be strongly involved also in the pathogenesis of autoantibody-related kidney glomerulopathies, leading to direct glomerular injury and recruitment of infiltrating inflammation pathways. More recently, unregulated complement activation has been shown to be associated with progression of non-antibody-mediated kidney diseases, including focal segmental glomerulosclerosis, C3 glomerular disease, thrombotic microangiopathies, or general fibrosis generation in progressive chronic kidney diseases. Some of the specific mechanisms associated with complement activation in these diseases were recently clarified, showing a dominant role of alternative activation pathway. Over the last decade, a growing number of anticomplement agents have been developed, and some of them are being approved for clinical use or already in use. Therefore, anticomplement therapies represent a realistic choice of therapeutic approaches for complement-related diseases. Herein, we review the complement system activation, regulatory mechanisms, their involvement in non-antibody-mediated glomerular diseases, and the recent advances in complement-targeting agents as potential therapeutic strategies.

Extrarenal determinants of kidney filter function

The kidney is an organ involved in cross talk with many human organs. The link between the immune system and the kidney has been studied in some detail, although data precisely elucidating their interaction are sparse, in particular with regard to the function of the kidney filter apparatus. Current research suggests that an understanding of the impairment of this cross talk between the bone marrow, as a fundament of the immune system and the kidney will provide meaningful insights into the pathophysiological mechanisms of impaired kidney filter function. Circulating factors have long been implicated in the pathogenesis of idiopathic nephrotic syndrome, particularly focal segmental glomerulosclerosis (FSGS) and its recurrence. Soluble urokinase receptor (suPAR) has emerged as a circulating factor responsible for FSGS and also as an early predictive marker for the development of various renal diseases. The bone marrow has recently been revealed as a predominant source of suPAR with deleterious effects on the kidney filter. These new findings have led to bone marrow or hematopoietic stem cell transplants being considered as potential therapeutic options for preventing the post-transplantation recurrence of FSGS or even as a treatment for the original disease associated with high suPAR levels. Whereas bone marrow transplantation for patients with pre-existing chronic kidney disease is challenging, recent clinical trials have demonstrated the promising outcome of combined bone marrow and kidney transplantation in patients with kidney failure. In this review, with its brief update on suPAR, we describe the critical new role of the bone marrow in the pathogenesis of the kidney disease process and the functional connection between these two organs through the soluble mediator, suPAR. We also comment on the feasibility of bone marrow transplants for the treatment of patients with chronic renal failure arising from recurrent FSGS.

Rituximab for Recurrence of Primary Focal Segmental Glomerulosclerosis After Kidney Transplantation: Clinical Outcomes

BACKGROUND

Rituximab has shown encouraging results for the treatment of kidney transplantation recipients with focal segmental glomerulosclerosis (FSGS) recurrence. However, the correct, opportune, and safe use of rituximab for this indication remains to be determined.

METHODS

This multicenter retrospective study reports on 19 new cases aged 35 (15-66) years who developed FSGS recurrence at 12 (1.5-27) days posttransplantation. Initial treatment consisted of plasma exchanges (PE), high doses of calcineurin inhibitors, and steroids. Rituximab was introduced either immediately (N = 6) or after failure of the initial treatment (N = 10) or failed attempted weaning from PE (N = 3).

RESULTS

Overall, we observed 9 of 19 complete remissions and 3 of 19 partial remissions. Estimated glomerular filtration rates (Modification of Diet in Renal Disease 4) were significantly higher in the responding patients than in nonresponding patients at month (M)12, M36, and M60. Overall, kidney survival at 5 years was 77.4% (95% range, 41.9-92.7). The 5-year graft survival rates in the responding patients and the nonresponding patients were 100% and 36.5%, respectively (P = 0.01). A further course of rituximab was required for 4 patients as a result of FSGS relapse, with good results. During the first year after renal transplantation, 14 patients developed severe infections (16 bacterial, 4 viral, 1 parasitic).

CONCLUSIONS

In kidney transplantation recipients with recurrent FSGS, rituximab therapy may be a recommended treatment for cases that have failed either the initial treatment or weaning from PE.

Optimal management of primary focal segmental glomerulosclerosis in adults

Focal segmental glomerulosclerosis (FSGS) is a frequent glomerular kidney disease that is revealed by proteinuria or even nephrotic syndrome. A diagnosis can be established from a kidney biopsy that shows focal and segmental glomerulosclerosis. This histopathological lesion may be caused by a primary podocyte injury (idiopathic FSGS) but is also associated with other pathologies (secondary FSGS). The first-line treatment for idiopathic FSGS with nephrotic syndrome is a prolonged course of corticosteroids. However, steroid resistance or steroid dependence is frequent, and despite intensified immunosuppressive treatment, FSGS can lead to end-stage renal failure. In addition, in some cases, FSGS can recur on a graft after kidney transplantation: an unidentified circulating factor may be implicated. Understanding of its physiopathology is unclear, and it remains an important challenge for the scientific community to identify a specific diagnostic biomarker and to develop specific therapeutics. This study reviews the treatment of primary FSGS and the recurrence of FSGS after kidney transplantation in adults.

Successful Preemptive Kidney Transplantation With Rituximab Induction in a Patient With Focal Segmental Glomerulosclerosis and Massive Nephrotic Syndrome: A Case Report

Primary focal segmental glomerulosclerosis (FSGS) recurs in 30% of patients receiving their first kidney transplant and often leads to graft loss. In the past, patients with FSGS and overt nephrotic syndrome rarely underwent transplantation. Rituximab (RTX), an anti-CD20-specific monoclonal antibody, was previously reported to be a valuable option in treating relapsing FSGS after kidney transplantation. We report here the first successful kidney transplantation in a young patient with primary FSGS and massive nephrotic syndrome treated with RTX induction. The patient was a 24-year-old woman who had developed nephrotic syndrome at the age of 4 years. FSGS was confirmed by results of a kidney biopsy, with subsequent treatment with cyclosporine and steroids, without remission. She was referred for a preemptive, deceased donor kidney transplant despite proteinuria levels reaching ∼10 g/d. She received induction therapy with 2 doses of RTX (375 mg/m²) at days 0 and 7, followed by tacrolimus 5 mg twice daily, mycophenolate mofetil 500 mg twice daily, and steroids after transplantation. Immediate kidney graft function was observed, with no proteinuria since day 13 posttransplant. The pretransplant soluble urokinase-type plasminogen activator receptor serum concentration was 4550 pg/mL; it decreased to 2191 pg/mL at day 13 and was 2073 pg/mL at 6 months' posttransplant. Thirty months after transplantation, the patient's serum creatinine level is 0.8 mg/dL, and no proteinuria has been observed. Successful kidney transplantation in a patient with pretransplant overt nephrotic syndrome secondary to FSGS, using rituximab as an induction therapy, is possible. Further recommendations for transplantation in such patients, however, should be based on results from larger clinical trials.